1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which a drive circuit is formed on a liquid crystal substrate.
2. Background Art
An active-matrix-type liquid crystal display device has been popularly used as a monitor of a personal computer, a television receiver set, an information display device of portable equipment or the like. The liquid crystal display device has the structure where a liquid crystal layer is sandwiched between a pair of substrates made of glass or the like on which pixel electrodes and counter electrodes are formed. By applying a voltage between the pixel electrodes and counter electrodes, the alignment direction of liquid crystal is changed. In this manner, by allowing the pixel electrodes and the counter electrodes to function as optical switching elements, an image is formed.
When the liquid crystal layer receives the application of the same voltage for a long time, the alignment direction of liquid crystal is fixed so that so-called burning occurs in the liquid crystal display device. To avoid this burning, in the liquid crystal display device, it is necessary to invert positive and negative polarities of a voltage applied to the liquid crystal layer for every fixed time, typically for every frame. Here, not only by alternately changing a voltage applied to the pixel electrode between two potentials consisting of a high potential and a low potential but also by alternately changing a voltage applied to the counter electrode between two potentials consisting of a high potential and a low potential, it is possible to decrease a width of the voltage applied to the pixel electrode thus reducing the power consumption.
As a method for changing a voltage applied to the counter electrode, several methods have been known. As such methods, a frame inversion method where voltages applied to all counter electrodes are set to the same potential, and the potential is changed for every frame, a line inversion method where a voltage having the same potential is applied to counter electrodes along a row (line) of pixels, and a voltage to be applied to the counter electrodes is changed for every row, a column inversion method where a voltage having the same potential is applied to counter electrodes along a column of pixels, and voltages to be applied to counter electrodes are changed for every column, a dot inversion method where voltages applied to counter electrodes of neighboring pixels are changed and the like are named. Among these methods, a line inversion method is superior to other methods in view of quality of an image display and easiness in forming a drive circuit.
JP-A-2006-276541 discloses a liquid crystal display device adopting a line inversion method where a counter electrode signal drive circuit is provided for every counter electrode signal.